A bladder pump is used to obtain water samples from ground monitoring wells. It may also be used for pumping hydrocarbons or other relatively low density liquids from an underground environment in which such liquids overlie and float upon the water in a water saturated formation. The pump is also used for recovering a representative water sample from beneath a floating layer of contaminant. An example of a pump of this type is disclosed in U.S. Pat. No. 4,886,432, issued to Kimberlin. This type of pump is driven by compressed gas and vacuum that are alternately supplied to the pump. Because this type of pump might be used in remote locations, there is, therefore, a need to provide a portable source of compressed gas and vacuum.